In recent years, attention has been given to a feed system (a non-contact feed system and a wireless charging system) that performs non-contact electric power supply (electric power transmission) to a CE device (Consumer Electronics Device) such as a mobile phone and a portable music player, for example. This makes it possible to start charging merely by placing an electronic device (a secondary-side device) on a charging tray (a primary-side device), instead of starting charging by inserting (connecting) a connector of a power-supply unit such as an AC adapter into the device. In other words, terminal connection between the electronic device and the charging tray becomes unnecessary.
As a method of thus performing non-contact power supply, an electromagnetic induction method is well known. In addition, in recent years, a non-contact feed system using a method called a magnetic resonance method utilizing an electromagnetic resonance phenomenon has also been receiving attention.
Currently, in non-contact feed systems using the electromagnetic induction method which have been already widely used, it is necessary that a feed source (a power transmission coil) and a feed destination (a power receiving coil) share a magnetic flux. Therefore, in order to perform power supply efficiently, it is necessary to dispose the feed source and the feed destination in proximity to each other, and it is also important to align axes in coupling.
Meanwhile, non-contact feed systems using the electromagnetic resonance phenomenon have such advantages that, due to the principle of the electromagnetic resonance phenomenon, electric power transmission is enabled over a longer distance than that in the electromagnetic induction method, and a decrease in transmission efficiency is small even when alignment of axes is poor to some extent. It is to be noted that concerning this electromagnetic resonance phenomenon, there is an electric-field resonance method, besides the magnetic resonance method. In a non-contact feed system of this magnetic-field resonance type (see, for example, Patent Literatures 1 and 2), precise alignment of axes is not necessary, and extending a feeding distance is also possible.